1. Field of Invention
The present invention relates to a paper supply mechanism that has a roll paper compartment for storing roll paper and supplies continuous printer paper from the roll paper compartment to the printing unit of a printer. The invention relates more particularly to a paper supply mechanism that enables the changing of the storage width of the roll paper compartment according to the paper width of the stored roll paper.
2. Description of Related Art
Roll paper printers used for issuing receipts, for example, use paper rolls having continuous printer paper wound into a roll as the recording medium. One type of roll paper supply mechanism used in such roll paper printers commonly uses a drop-in type roll paper compartment into which the paper supply roll is loaded from above and which allows the paper roll to rotate freely. Japanese Unexamined Patent Appl. Pub. JP-A-2006-44900 teaches a roll paper supply mechanism of this type that enables adjusting of the paper storage width by moving the left and right side walls that determine the storage width of the roll paper compartment.
With a drop-in type roll paper compartment, the inertial load of the roll paper and the friction between the roll paper and the bottom of the roll paper compartment must be overcome in order to make the roll paper roll deliver the paper from the roll paper compartment. The roll paper is fed by driving a paper feed roller disposed in the paper transportation path. The paper transportation load on the paper feed rollers increases as the paper speed increases, and can cause slippage between the paper feed roller and the paper, and which reduces paper transportation precision. To reduce the paper transportation load and enable conveying the paper precisely, Japanese Unexamined Patent Appl. Pub. JP-A-2007-203563 teaches a roll paper supply mechanism disposed to the bottom of the roll paper compartment that has a delivery roller for causing the roll paper to turn in the feed direction.
In the roll paper supply mechanisms of the related art described above, the side walls of the roll paper compartment can move. The side walls of the roll paper compartment are manually moved to positions corresponding to the paper width of the stored paper roll to adjust the storage width. However, because there are deviations in roll paper width and the roll paper supply mechanism, the storage width must be adjusted to accommodate these deviations.
If the storage width is too narrow after being adjusted, the side walls will push forcefully against the ends of the roll paper. This results in an excessive paper transportation load acting on the paper feed roller of the roll paper printer, for example, and therefore requires even greater force to deliver the printing paper from the paper roll.
However, if the storage width is too wide after being adjusted, the roll paper can shift side to side inside the roll paper compartment, which can result in the roll paper meandering or becoming skewed as it is delivered into the paper transportation path.
When a delivery roller is disposed in the roll paper compartment, the delivery roller is generally made from rubber or other material with a high coefficient of friction. In order to move the roll paper sideways (that is, along the width of the roll paper compartment) while in contact with the delivery roller while also moving the side walls, the roll paper must be pushed with enough force to overcome the friction between the roll paper and other parts when the paper roll is placed in the roll paper compartment and the side walls are then moved to adjust the width.
In addition, when the roll paper is on the delivery roller and the roll paper is shifted to one side, side pressure from friction with the delivery roller when the roll moves acts in addition to the side pressure from the side walls of the roll paper compartment, and the paper transportation load required to feed printing paper from the paper roll becomes excessive.